Related Clues:

• ''Das Boot,'' for one
• Liner threat, once
• World War II sub
• "The Enemy Below" threat
• Convoy chaser
• WWII submarine
• Sub with sauerkraut?
• W.W. II blockade enforcer
• Destroyer hunter
• Torpedo launcher
• WW II sub
• WWII blockade vessel
• W.W. II Atlantic lurker
• WWII ship sinker
• Destroyer's foe